Johanj said:
It is only under braking, when accelerating or just driving/coasting it is smooth, the shudder decreases with speed, have been told it might be tyres?
Tyre flat spots also create a shudder/vibration which are normally noticeable around 120km/h - 140km/h, and they will give a slight vibration that will lessen as your speed decreases.
But since you say that you only get it under braking, then I'm a little confused. Flat spots will make it shudder all the time AFAIK.
Do you still have the original rims on?
Also to add, wheel balancing, buckled/bent rims, and tyre flat spots, all create a shudder. However, they will shudder all the time and not only under braking. Have you checked any of these things yet?
Shudder under braking is normally warped discs AFAIK. So maybe the new discs have warped as well. With all the rain it might be the case, because warped discs are caused by vast changes in temperature, like driving through a puddle when your brakes are extremely hot.
Firstly I would go to a quality tyre place and get them to check the tyres for flat spots, check the rims for buckles/dents & cracks, and get them to redo balancing and alignment. If this doesn't sort out the problem, then you might have to have the discs skimmed.
Where are you situated bud?